Uranium(III) chloride

Uranium(III) chloride , UCl₃, is a chemical compound that contains the earth metal uranium and chlorine. UCl₃ is used mostly to reprocess spent nuclear fuel. Uranium(III) chloride is synthesized various ways from uranium(IV) chloride; however, UCl₃ is less stable than UCl₄.

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Preparation

There are two ways to synthesize uranium(III) chloride. The following processes describe how to produce uranium(III) chloride.

(1) In a mixture of NaCl-KCl at 670-710 °C, add uranium tetrachloride with uranium metal.

3UCl₄ + U → 4UCl₃^[1]

(2) Heat uranium(IV) chloride in hydrogen gas.

2UCl₄ + H₂ → 2UCl₃ + 2HCl^[2]

Properties

In the uranium(III) chloride molecule, three chlorine atoms are bonded around a uranium center in a tricapped trigonal prismatic configuration. A tricapped trigonal prismatic configuration has a configuration number of nine.

Uranium(III) chloride is a green crystalline solid at room temperature. UCl₃ melts at 837 °C and boils at 1657°C. Uranium(III) chloride has a density of 5500 kg/m³ or 5.500 g/cm³.

Its composition by weight:

Chlorine: 30.84%

Uranium: 69.16%

Its formal oxidative states:

Chlorine: −1

Uranium: +3

Uranium(III) chloride is very soluble in water and is also very hygroscopic. UCl₃ is more stable in a solution of hydrochloric acid.^[3]

Uses

Reagent

Uranium(III) chloride is used in reactions with tetrahydrofuran (THF) and sodium methylcyclopentadiene to prepare various uranium metallocene complexes.^[4]

Catalyst

Uranium(III) chloride is used as a catalyst during reactions between lithium aluminum hydride (LiAlH₄) and olefins to produce alkyl aluminate compounds.^[5]

Molten form

The molten form of uranium(III) chloride is a typical compound in pyrochemical processes as it is important in the reprocessing of spent nuclear fuels.^[6]UCl₃ is usually the form that uranium takes as spent fuel in electrorefining processes.^[7],^[6]

Hydrates

There are three hydrates of uranium(III) chloride:

1. UCl₃^.2H₂O^.2CH₃CN
2. UCl₃^.6H₂O
3. UCl₃^.7H₂O

Each are synthesized by the reduction of uranium(IV) chloride in methylcyanide (acetonitrile), with specific amounts of water and propionic acid.^[8]

Precautions

While there are no long-term data on the toxic effects thas UCl₃, it is important to minimize exposure to this compound when possible.

Similar to other uranium compounds that are soluble, UCl₃ is likely absorbed into the blood through the alveolar pockets of the longs within days of exposure. Exposure to uranium(III) chloride leads to toxicity of the renal system.^[9]

References

1. ^ Serrano, K.; Taxil, P.; Dugne, O.; Bouvet, S.; Puech, E. J. Nucl. Mater. 2000, 282, 137–145.
2. ^ Remsen, Ira. Inorganic Chemistry. New York: Henry Holt and Company, 1890.
3. ^ Comey, Arthur M. and Hahn, Dorothy A. A Dictionary of Chemical Solubilities: Inorganic. New York: The MacMillan Company, 1921.
4. ^ Brenna, J.G.; Anderson, R.A.; Zalkin, A. Inorg. Chem. 1986, 25, 1756–1760.
5. ^ Le Marechal, J.F.; Ephritikhine, M.; Folcher, G. J. Organomet. Chem. 1986, 309, C1–C3
6. ^ ^{a b} Okamoto, Y.; Madden, P.; Minato, K. J. Nucl. Mater. 2005, 344, 109–114.
7. ^ Okamoto, Y.; Kobayashi, F.; Ogawa, T. J. Alloys Compd. 1998, 271, 355–358.
8. ^ Mech, A.; Karbowick, M.; Lis, T. Polyhedron. 2006, 25, 2083–2092.
9. ^ Bertell, Rosalie. "Gulf War Veterans and Depleted Uranium." May 1999. Available: http://ccnr.org/du_hague.html